1. Field of the Invention
The present invention relates to a construction machine having a cab installed on the top of a floor plate.
2. Description of the Related Art
FIG. 3 shows a side view of a conventional hydraulic excavator, as one example of the construction machine. In FIG. 3, the hydraulic excavator comprises a lower travel body 51 provided with a pair of crawlers, an upper rotating structure 52 rotatably mounted above the lower travel body 51, and an attachment 53 mounted for vertical pivotal movement at the front of the upper rotating structure 52. The upper rotating structure 52 is constituted such that a cab 54, an engine, a counterweight and so on are mounted on a machine frame 61. The interior of the cab 54 is provided with an operator's seat, and with a front window on the surface thereof, so that an operator seated on the seat controls the operation of the attachment 53 while looking forward through the front window. Recently, the conventional cab 54 is equipped with an air conditioning unit in order to improve habitability in summer and winter.
The interior of the cab 54 is shown schematically in FIG. 4. In FIG. 4, an air conditioning unit 56 is mounted at the rear of the upper surface of the floor plate 55. An operator's seat 57 is mounted in the central portion of the upper surface of the floor plate 55. In the construction machine such as a hydraulic excavator, since an operator seated on the operator's seat 57 overlooks the work environment through the front window provided at the front part of the cabin 54, it is desired that the front window be as wide as possible. Because of this, the air conditioning unit 56 is normally installed at the rear of the operator's seat 57.
Cool air A or warm air B produced by the air conditioning unit is blown out of a blowing opening for the face 58, a blowing opening for the feet 59, and a blowing opening for the back 60. Since generally, cool air moves down and warm air moves up, the cool air A is mainly blown out of the blowing opening for the face 58 and the blowing opening for the back 60, and the warm air B is mainly blown out of the blowing opening for the feet 59.
One example of the procedure for installing the cab 54 on the floor plate 55 will be explained. Conventionally, in the state in which the operator's seat 57 and the air conditioning unit 56 are mounted on the floor plate 55, the cab 54 lifted from top by a crane or the like is placed on the floor plate 55, and the cab 54 is locked to the floor plate 55, after which ducting and wiring are connected. In case having the blowing opening for the face 58 shown in FIG. 4, the duct for connecting the blowing opening for the face 58 with the air conditioning unit 56 has been mounted by an assembly worker who enters the cab 54 after the cab 54 has been locked to the floor plate 55.
As prior art showing a duct construction for an air conditioning unit within a cab, an arrangement has been known in which the duct directed at a blowing opening of the air conditioning unit at the front part is in integral form that cannot be divided along its length.
Incidentally, conventionally, work for connecting various wiring and a ducts for installing the cab 54 on the floor plate 55 is carried out by a worker who enters the narrow cab 54, thus posing a problem that the work becomes cumbersome and difficult. Particularly, the blowing opening for the face 58 must be mounted on the cab 54 side instead of the floor plate 55 side in terms of restriction of the arranging position thereof. Therefore, piping work of the duct for connecting the air conditioning unit 56 mounted on the floor plate 55 with the blowing opening for face 58 mounted on the cab 54 must be carried out when the cab 54 and the floor plate 55 are installed. This work is not easy because it is done in a narrow place, and therefore, the production time becomes long.
Further, it has been recently desired, in order to improve viewing and working properties in rainy weather or in cold weather, that a blowing opening for defrosting is provided around the front window for removing fogging of the front window. In this case, duct piping for the blowing opening for defrosting in addition to the duct piping for the blowing opening for the face 58 is necessary, thus the problem which occurs with the aforementioned duct piping work becomes more notable.